Removal of mercaptans from gasoline



ZOFDJOW mmnOU QmUDQmm S.ClCARNEY ATZO/QNEKS' J. A. MCBRIDE ET AL REMOVAL OF MERCAPTANS FROM GASOLINE April 11, 195o Filed April 27, 1949 April 11, 1950 J. A. MCBRIDE ET AL REMOVAL oF MERCAPTANS FROM GAsoLINE 2 sheets-sheet 2 Filed April 27. 1949 APatented Apr. 11, 195o UNITED STATES PATENT oFFlcE REMOVAL OFMERCAPTANS FROM GAsoLlNE f .101m A. Mamme, Phillips, Tex., and sama'l o. Carney, Bartlesville, Okla., assignors-tovPhillips- Petroleum Company, a corporation cf l )elavvare application Aprile?, 1949, serialN11-89,948lI invention relates tothe chemical treat?l ment of gasoline. In one of itsfaspects the invention relates to the removal of mercaptans (sulfur compounds) from gasoline. aspects theinvention'relates to the use of a. novel treating agent which will convert mercaptans ingasoline to mercaptides which are soluble in said agent,'thesubsequent separation of which from the gasoline will separate from said gasoline the undesired mercaptans in said converted orv dissolved mercaptideiorm.v In another of its aspects the invention relates to the use of a novel treating solution to remove mercaptides from a gasoline which has been treated in a conventional manner with a reagent comprising cupric and c'u'prous chlorides.' In one embodiment of the invention an aqueous glycol ether-cuprous chlo-v ride reagent is employedasthe treating agent, as more fully set forth and described below. In another embodiment of the inventionan aqueous solution of a glycol ether is used as the treating solution. 7

`In the usual"desulfurizing process the mercaptans in the gasoline are converted to' disulfldes. These'being gasoline-soluble remain in the gasoline'. Thus', the product is marketed containing sulfur compounds which it wouldy be highly ,de-

sirable to remove efficiently in a readily and economically 'feasible' manner.

' We` have found that the ionization constant of cuprous mercaptide is so low that the reaction between' cuprouschloride. and mercaptan iszsubstantially completed even when the meri' captan is present in great dilution vin a considera-A ble volume of gasoline. Also', We have found'that both'the cuprous mercaptides and cuprous chloride aresuciently soluble in aqueous glycol ether-cuprous chloride reagentto convertmercaptans in gasoline to mercaptides and to remove" the thus `formed mercaptides therefrom. l

Thus, We have found that uponl contacting aqueous glycol 'ether-cuprous chloride reagent.' with`ga`soline,'it 'wi-llconve'r-t the mercaptan' con` tent thereof substantially to cuprous mercaptides" and also that these-'mercaptides yare suiciently soluble in said lreagent in the presence of.. the gasoline vto "cause the mercaptides substantially to be taken into said reagent and out from the gasoline'. Thus, we have found that the mercap' tan content of" a1-gasoline can be .converted-and removed Atheref-ioniby 'reacting the mercaptans" with cuprousv chloride to form cuprousmercap- In another of its,.-

13 claims, (o1. 419t- 30) l tides andthen Vdissolving said cuprous .merca-p# 1 tides in aglycol etherfcontaining solution.v :f: The treating agent containing the cuprousmercaptides can be subjected to oxidation conditions `to convert. said mercaptides to corresponding diff After separation; 0f ythese disuldes from thetreating agent, it. can.: be treatedwith amercaptan to form corresponde-.r

suldes and to cupri'c chloride.

ing disulfdevand to-rjeform cuprous chloride;`

The disulfdes can be separated from the treating agent and the latter .canbe re-used'inl the initial".y

contacting zone. i 1. f .15. Thus, according tov this invention, there is pro-1v vided a process bymeans of which the mercaptans present ina gasoline are not' only converted to]-v disulfides but also ajprocess by means of which the disulfide derivatives of the mercaptans in the .T

which mercaptans are removed from a gasoline,

thereby desulfurizing` saidQgasoline, in a manner superior to the usual method which merely con#l verts the mercaptans-,to disulfides which remain soluble and dissolvedv in the gasoline, and lbymeans of which disuldes are produced in a marketable condition as a bi1-product of the process;

Hence, the-undesirable mercaptans in the gasQ-rline are converted to desirable disuldes, sep arate andapart from said gasoline.

In an alternative-,embodiment the invention,v may bepracticed as an improvement uponconr ventional coppertreating"processes wherein substantial (usually small) amountsof copper mercaptides', formed unintentionally but unavoidablyin the treatingstep,are present in-solution inthe treated gasoline and must bere-moved therefrom because of their corrosive rnature.- In this eine 4 bodiment the vcopper mercaptide-containing gasoline is Washed With an aqueous glycol ether;l solution, and the mercaptides are thereby removed from the gasoline. This results in a partial Ole-1;, sulful-i'zation ofthe conventionally'copper treatead.v and swee tenedv gasoline?.- The ,glycol ether-soy` lution may then be oxidized to convert, the mer captides todisulfide;whichj are readilyseparated from the glycol-ether solutionv as described-here v4 inafter, and simultaneously convert the copper to `v cupric chloride Whichremainsdissolved in the. glycol ethersolution." .The glycol ether may then;`r be recovered yby-distillation `for-,reuse in the proc-f; ess. Alternatively,- the .glycol ether may` be sep?,4

copper which is expensive in view of the necessity of disposing ultimately of large quantities of cuprous chloride.

Therefore, as an added feature of this invention, the treating solution, after disuldes are separated from it in separation zone 9, is treated with a mercaptan in reduction zenev i@ to reduce cupric chloride to cuprous chloride. Mercaptans will react with the cupric chloride to reduce the cupric ion to cuprous ion with concomitant production of disulides from the mercptan. The merthe drawings in which are shown two diagrammal tic embodiments of integrated processes according to the invention.

In Figure 1, gasoline containing mercaptans to be removed therefrom'is contacted in contacting n zone 1 with an aqueous glycol ether-cuprouschloride treating agent. y

The concentration ofthe cuprous chloride in the treating reagent can: be varied. However, it

is -now preferred to use a: treatingvsolution satu-irated, or nearly saturated, with cuprous chloride. The.- proportion of the glycol ether relative to that of the water canbev varied'. However, it is now preferred to operate with about 85%-95% glycol' ether and' 15 L7t-5.% water. As` glycol ether there can be employed the monoalkyl ethers of ethylene glycol or diethylene glycol. The alkyl group should contain, preferably, one to four carbon atoms. One. skilled in the art can readily determine ay glycol ether for use in the process of the invention by mere routine test'.y It; should befnoted that the larger the alkyl group, the higher will be the solubility of the gasoline in the glycol ether.v Also, itvisf noted that the nature of the gasoline will aect to an extent its solubility in the glycol ether.. Generally, the more aromaticthe gasoline, the higher will beits solubility in the glycol ether..` Presently preferred Ias glycol ethers to be employed according to the invention are methyl Carbitol (diethylene glycol :n.oriomethyl ether) and methyl Cellosolve (ethyL ene glycol monomethyl ether).

. Theftemperature in the contacting zone is preferably maintained in the. approximate range of 50 F.160 F.

" In the contacting zone the treating agent turns a dark claret color. From thiszone, the gasoline and treating solution are transferred to settling zone 2 wherein the gasoline and treating solu tion form` two layers. The gasoline is passed to wash zone 3 wherein: it is thoroughly washed with water, after whichl itis allowed to settle in set'- tling zone 4 wherein water is separated. therefrom. The gasoline is then clay-treated in clay vlter zone 5 and is now ready for marketing.

Treating or reagent solution separated from the gasoline in settling zone 2J is removed therefrom and. passed tov spent reagent surge Zone'. 6,.

In order to regenerate the treating solution or reagent, at least-a portion ofit can be withdrawn continuously from zonev 6 and passed to oxidation zone 8 wherein it can be blown with air to convert the cuprous mercaptides to cupric chloride and disuldes. Thus, in zone 8 the treating solutonzcan be air'blown in the-presence of' hydrogenvchloride vuntil all mercaptide has been oxidized:

to disulde.

It :is possible to reduce the cupricl chloride-to.

i cuprous chloride using metallic copper. However;

captan used in reduction Zone I0 is selected preferably from the alkyl mercaptans containing 1-4 carbon atoms. The; spent treating solution is treated with the mercaptan until it turns a pale straw yellow' color. Thus, by separating the disulde formed and recycling the reduced treating solution to the contacting zone to treat further quantities of gasoline, the volume of treating solution is maintained substantially constant and the disposal problem encountered usingv copper is entirely' eliminated.

The mercaptans" used in zone I0 to reduce: they oxidized reagentA can,4 if desired, bey derived from the disulides produced in Oxidation zone 8 and withdrawn from4 separation zone: 9; or from disulcles fromv another source within or without the system. The conversion of the 'clisuldes to mer'- captans can be eiected. by thermal decomposition of the disulfides or, preferably, by' treatment with hydrogen in presenceA of a. sulfactive hydrogena-V` tion catalyst. Y

From reductionl zone I0: the treating solution is passed to light hydrocarbon wash zone IIf and then to separation Zone i2 in. which zones it iswashed and readied for reuse. From zone. I2 the reshened treating solution isv passed into Zone 1 andfrom there reused as described above. A function of zones- I I and I2 is toseparate-disul-.-

i fides from the treating solution. 'I-hisv is accom-- .plished by solution of the disuldes in the hydro-A carbon washing material from which the disuldes can theny be covered' in stripping zone I3 and distillation zone I4. The disulde fraction obtained in zone 9 is advantageously also treated in zones I3 and Ill or it may be recovered separately byl means not shown. Thus it is that in. this embodiment of the invention,I there hasl beenprovided a unitary process for the removal of sulfur from gasoline; and for its recovery as marketable disulfide.

As an alternativel withiny the scope of, the invention here disclosed a mercaptan-containing gasoline can be used as the reducing. agent in zone I0. When such a reducing agent is used, the eflluent from zone IB can be passed directlyk to zone I2A from whichy regenerated' reagent is removed: `as a lower phase and the gasoline is. removed as an upper phase; line and can be marketedas suohthatis, a gaso line. in. which the mercaptans, .have been comA verted to disulfldes; (as distinguished from the desulfurized. gasoline withdrawn from zone 2).. When the immediately Ipreceding, step is employed, no mercaptans, otherthan'- those in the gasoline employed in said4 step;y need. be, supplied tozonelil. Y

As another alternative within, the: scope. of the invention themercaptan's, usedrir zone L0 of thisY process, can be recovered from the steam strip ping cfr spent caustic which has been used-.to treat. sulfur containing1 p1t0d11cts as inthe oil reiinery or, as a further alternative.- a. stream of. refinery vapors, comprising Gegend. lighter compounds.-

contaning methyl and ethyl mercaptans-canbe- This gasoline. is a sweetenedV gasa cuprous chloride reagent in separate stages, using' partially spent reagent in a rst stage and fresh reagent in a second stage. Thus, in the embodi ment shown diagrammatically in Figure 2 the gasoline is ilrst contacted in `contacting zone I with partially spent reagent derived from a subsequent contacting stage. The mixture of gasoline and reagent is lpassed to settling zone 2, from which spent reagent is withdrawn and passed to spent reagent surge zone 6 while the separated gasoline is passed to contacting zone Ia. Here the gasoline is contacted with fresh or regenerated glycol ether-cuprous chloride reagent and the mixture is passed to settling zone 2a. Partial# ly spent reagent is separated from the gasoline in zone 2a and passed directly into contacting zone I as described hereinabove, and the gasoline is passed to further treatment just as in the embodiment of Figure 1. Spent reagent is passed from zone 6 rto oxidation zone 8 and subsequent regeneration steps, and regenerated reagent is returned to zone 1, as in Figure 1.

In the process of this invention the mercaptides as formed are dissolved and remain dissolved in the treating solution. Thus, there is encountered no precipitation problem.

In the embodiment wherein the invention is practiced in conjunction with a conventional copper sweetening process, for the removal of dissolved copper mercaptides from the treated gasoline, the treated gasoline is contacted, in a contacting zone like zone I of Figure 1, with an aqueous glycol ether solution. 'I'his solution differs from the reagent of Figure 1 only in that it contains no copper compounds, or at least is substantially free therefrom. The copper mercaptides are selectively dissolved by the glycol ether solution, so that the gasoline removed from a subsequent separation zone has been partially desulfurized and, more important, is free from the corrosive copper mercaptides formed in the copper treating step. Disuldes, formed in the conventional copper treating step by oxidation of the mercaptans, are of course still present in solution in the gasoline. While this embodiment of the invention is generally less preferable, because the resulting gasoline although sweet is only partially desulfurized, it nevertheless provides a worthwhile addition to existing copper sweetening units by enabling them to be operated so as to eliminate copper mercaptides from the treated gasoline without the consumption of an additional reagent (e. g., sodium sulfide) for this purpose. Ths glycol ether solution is readily recovered for reuse in the process as described hereinabove.

The following example is illustrative f the invention: .1.

Example Twenty-ve milliliter portions of a catalytically cracked gasoline, soured by the addition of 0.3 per cent mercaptan sulfur in the Vform of a. mixture of synthetic tertiary mercaptans, were shaken with 25 milliliters 0f cuprous ehloridefmethyl Car' mined by a standard titration employing a pyridine-type indicator. Four such portions of soured gasoline were treated with the same portion of reagent; the fourth portion showed no mercaptan sulfur indicating the reagent was still satisfactorily active. Treatment of the desulfurized gasoline with zinc dust and acetic acid produced no titratable mercaptan sulfur, indicating the absence of disulflde'in the treated gasoline. Re. oxidation of the used reagent caused liberation of the extracted mercaptans in the form of disulfide.

Reasonable variation and modification are possible within the sco-pe of the appended claims to the invention, the essence of which is that a process for the treatment of a sulfur compound containing gasoline has been set forth by means of which it is possible to substantially completely remove the sulfur compounds from said gasoline in a readily feasible and, if desired, cyclic manner, with recoveryof the sulfur compounds as disuldes in marketable form, employing in the process a solution of cuprous chloride dissolved ina water solution of a glycol ether or by means of which a conventionally sweetened gasoline can be treated to remove at least a part of the sulfur col ether containing-solution, and separating saidv gasoline from said glycol ether-containing solution.

3; A process for treating gasoline type hydrocarbon's` to remove mercaptans therefrom which comprises contacting said hydrocarbons with a treating agent essentially consisting of an aqueous glycol ether-cuprous chloride reagent and then separating said treating agent from said gasoline.

4. A process for treating gasoline type hydrocarbons to remove mercaptans therefrom which comprises contacting said hydrocarbons with a treating agent essentially consisting of an aqueous glycol ether-cuprous chloride reagent to convert said mercaptans to cuprous mercaptides and to dissolve said mercaptides in said treating agent; separating said treating agent from said gasoline; subjecting said treating agent to oxidation conditions to convert the mercaptides therein to corresponding disulfides and to cupric chloride and then separating said disuldes from said treating solution and the system as a product of the process.

5. A process for treating gasoline type hydrocarbons to remove mercaptans therefrom which comprises contacting said hydrocarbons in an initial zone with a treating agent essentially consisting of an aqueous glycol ether-cuprous chloride reagent to coni/crt said mercaptans to cuprous mercaptides and to dissolve said mercaptides? in said treating agent; separating said.- treating agent from said. gasoline; subjecting said.

treating' agent to oxidation conditionslto convert the mercaptides therein to corresponding disul-` des. and to cupric chloride; and then separating saidl disulfides from said*v treating solution andthe system as a product of the process; then reacting said treating solution containing cuzpric chloride with a mercaptan to form the corresponding disuldes and to reform `cuprous chloride; separating said disuldes fromf said last mentioned treating solution and from the system as another product ofv the process and passingv said treating solution containing the reformed. cuprous chloride-.to the initial contacting zone;

6. A process for treating gasoline type hydrocarbons to remove mercaptans therefrom which comprises contacting said hydrocarbons in an initial zone with a treating agent essentially consisting of an aqueous glycol ether-cuprous chloride*y reagent to convert. said mercaptans to cupr'ous mercaptides and to dissolve said mercaptides in said treating agent; separating said treating agent from said gasoline; subjecting said treating agent` to oxidation conditions to convert the mercaptides therein to corresponding disulfides and to cupric chloride; and then separating said'. disuldes from. saidv treating solution and converting said disuldes to mercaptans; then reacting said treating solution containingV cupricv chloride with said mercaptans to form the corresponding disulfides and to reform `cuprousl chloride; separating said disulde from said last mentioned treating solution and from the system as a productor` the process.; and passing. said treating solution containing the reformed cuprous chloride tothe initialV contacting zone.

' 7:. A process for treating gasoline type hydrocarbons to remove mercaptans therefrom which comprises contacting said hydrocarbons in an initial zone with a treating agent essentially consisting of an aqueous glycol ether-cuprous chloride reagent to con-vert said mercaptans to cuprous mercaptides and t-o dissolve said mercaptides in said treating agent; separating said treating agent. from said gasoline; subjecting said treating agent to oxidation conditions to convert themercaptides therein to corresponding disu1 des and to cupric chloride; and then separating said disuldes from. said treating solution and the system as a productV of the process; then re.- acting said, treating solution containing cupric 8 chloride: with a mercaptan-containing gasoline, to form the corresponding disuldes therein and.' to reform cuprous chloride in said treating solution; sepa-rating a sweetened gasoline from said. treating solution as a product of the process; and.

passing said treating solution containing the reformed cuprous chloride to the initial contactingv zone.

8. The oxidation of an aqueous glycol ether--v cuprous chloride treating agent which has been used to treat. a gasoline to convert mercaptans in saidgasoline to mercaptides and which agent contains said mercaptides. to. convert said mer :captides to corresponding disuldes and cupric chloride.

9. Theprocess of claim 8 wherein the oxidation isfeiected -in presence of hydrogen chlorideV by blowing withv air.

19. The process of claim 3 wherein the glycoll ether solution in Water contains 80%- to 95%- glycol ether, is substantially saturated with cuprous chloride and the treatment is eiected at a temperature in the range v50" F. to 160 F.

11. The process of claim 3 wherein the glycol ether is ethylene glycol monoznethyl ether.

12. The process of claim 3 wherein the glycol; ether is diethylene glycol monomethyl ether.

13. In a process for sweetenin'g a mercaptan.-A containing gasoline wherein the gasolinev isA treated with a reagent comprising cujpricv and cuprous chlorides for the Y conversion of said mercaptans to corresponding -disulfides, and' wherein gasoline soluble copper mercaptides are produced concomitantly, the improvement which comprises. separately contacting said treated gasoline with an aqueous solution of a glycol ether whereby said copper mercaptides are removed` from said gasoline, and separating the gasoline from the glycolether solution. v

JOHN A. MCBRIDE. SAMUEL C. CARNEY.

REFERENCES CITED The following references are of record in the; le of this patent: v

UNITED STATES PATENTS Bond et a1 Mar. a, 1949 

1. A PROCESS FOR TREATING GASOLINE TYPE HYDROCARBONS CONTAINING MERCAPTANS COMPRISING REACTING AT LEAST A PORTION OF THE MERCAPTANS WITH CUPROUS CHLORIDE TO FORM CUPROUSD MERCAPTIDES AND DISSOLVING SAID CUPROUS MERCAPTIDES IN A GLYCOL ETHER CONTAINING SOLUTION, AND SEPARATING SAID GASOLINE FROM SAID SOLUTION. 